Researchers use transoceanic fiber hyperlink for geophysical sensing

WASHINGTON — In a brand new research, researchers present that the fiber optic cables that carry knowledge the world over’s oceans can be used to sense geophysical occasions and monitor ocean and seafloor circumstances.

Although buoys and cabled observatories can be utilized to watch components of the ocean, the data they supply is proscribed to their instant environment. The new strategy may provide a manner to make use of the worldwide community of subsea fiber optic cables to check in any other case inaccessible components of the ocean.

“Once perfected, this new technique will allow geophysical sensing in the ocean depths, which are largely unexplored because of a lack of instrumentation that works in this environment,” mentioned Zhongwen Zhan, assistant professor of geophysics at Caltech. “It could one day be used to detect earthquakes with epicenters in the ocean, allowing earlier warnings of earthquakes and tsunamis, for example.”

In Optica, The Optical Society’s journal for top impression analysis, Zhan, along with researchers from Google and the University of L’Aquila exhibit that the brand new strategy can detect earthquakes and ocean swells–collections of waves produced by storms. They did this utilizing the Curie transoceanic fiber optic cable that connects Los Angeles, California with Valparaiso, Chile.

Going past carrying knowledge

The new approach makes use of the truth that earthquakes, strain variations or different adjustments within the atmosphere of a transoceanic cable create delicate adjustments within the mild touring down the optical fibers. Although transoceanic fiber optic hyperlinks have been used to sense geophysical occasions within the Mediterranean Ocean, the strategy utilized in earlier demonstrations required extraordinarily specialised lasers which are troublesome to acquire and use.

“We used standard telecommunications equipment without any extra optical components other than those already present in commercial transceivers,” mentioned Zhan. “In addition, there is no need for a dedicated light channel because the data required for sensing can be collected without disturbing the regular operation of the optical transmission system.”

Most transoceanic cables use subtle coherent mild strategies to encode knowledge in each the amplitude and section of the transmitted mild. To analyze adjustments within the mild touring down the cable, the researchers developed a theoretical framework for utilizing the polarization knowledge generated by a coherent transmission system for sensing within the deep ocean. The technique they developed measures tiny adjustments in polarization of the transmitted mild.

“Any changes in the environment of the cable will induce a tiny, but detectable difference in the light’s polarization,” mentioned Zhan. “We developed the theoretical framework required to interpret polarization data in submarine cables, which will enable further quantitative understanding of submarine geophysical processes.”

Putting the idea into follow

The researchers used their new strategy to detect deep-sea earthquakes and ocean swells primarily based on readings acquired from the Curie transoceanic fiber optic cable. The measurements agreed properly with impartial measurements made with seismometers on land.

“The stability of the polarization in the Curie submarine system is so high that we were able to detect differential changes in the optical path length of two light polarizations of just 1.5 microns over the entire length of the cable,” mentioned Zhan. “This equates to just a fraction of the wavelength for the laser light traveling down the cable.”

The researchers are nonetheless working to higher perceive how you can use the polarization knowledge to detect numerous adjustments within the atmosphere for an undersea optical cable.


Paper: A. Mecozzi, M. Cantono, J. C. Castellanos, V. Kamalov, R. Muller, Z. Zhan, “Polarization sensing using submarine optical cables,” Optica, 8, 6, 788-795 (2021).


About Optica

Optica is an open-access, journal devoted to the fast dissemination of high-impact peer-reviewed analysis throughout your entire spectrum of optics and photonics. Published month-to-month by The Optical Society (OSA), Optica gives a discussion board for pioneering analysis to be swiftly accessed by the worldwide neighborhood, whether or not that analysis is theoretical or experimental, basic or utilized. Optica maintains a distinguished editorial board of greater than 60 affiliate editors from world wide and is overseen by Editor-in-Chief Prem Kumar, Northwestern University, USA. For extra info, go to Optica.

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the main skilled group for scientists, engineers, college students and enterprise leaders who gasoline discoveries, form real-life purposes and speed up achievements within the science of sunshine. Through world-renowned publications, conferences and membership initiatives, OSA gives high quality analysis, impressed interactions and devoted assets for its in depth international community of optics and photonics consultants. For extra info, go to

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